Manifold Longevity
 

Hi everyone – Happy New Year!

We have a 2000 (Gen 6) 7.4 MPI with approximately 500 hours. 2 years ago the Starboard manifold developed a very small hairline crack above a “star” bolt. I replaced the manifold without issues. I was just at our boat today and noticed that there is a little antifreeze in the bilge and I can feel a “wet spot” now on the Port Manifold. I don’t know if there are any cracks in the manifold etc., It could be as simple as a loose drain plug. I couldn’t get much of a look. I have the marina winterize the boat. My question this boat has been 100% fresh water -- Should I have replaced both manifolds at the same time- and if so how long do these typically last?

Thanks and just think around 18 weeks until boating (up north)

3pointstar

I just cut one dry joint manifold in half salt water after 7yrs still looked great only putting one new one back on.

Since you say antifreeze in the bilge, I assume you have closed cooling. If its a full system, the manifolds would be cooled with antifreeze and should basically last forever unless they were overheated or something.

Not closed cooling

The antifreeze is put in during the winterization done by the marina. There never was any overheating by any stretch of the imagination. It was really bizarre on the other manifold. There was a star/hex bolt on the medial side and right above it was a very slight crack. I'm suspecting some similar has happened on the starboard side. The engine has always ran within temp ranges and I'm anal about the impeller replacement. Like I said it could be as simple as a loose drain plug.

Thanks for the response

3pointstar

First thought is whoever did the winterization screwed something up and or cracked a hose. The Fitting that goes into the bottom of the manifold can be fragile in cold weather and the drain screw that goes in the bottom of that fitting can crossthread or just fail. Second is I always replace manifolds in pairs, thats just me.

Chris

Chris thank you so much for the reply.

I went to the boat today with flashlight and mirror -- I can't see much of anything - it looks somewhat like the antifreeze may have leaked out of the fitting threads that screw into the bottom of the manifold. Or there could be a crack towards the top that I just can't see. In any case what I'm going to do is wait until spring (which can't come soon enough) and start it up and look of there is an "steam" coming out of the manifold in that area. Also, I thought that I would just order a new fitting and install- If the manifold is truly bad I'll need a new fitting anyway.

As a side bar - I have a friend that is an old mechanic - He's in his 70's. When I showed him my old manifold with the hairline crack he said that I should just replace the other one now -- if one goes the other one will -- I guess wisdom does prevail!

Again, thanks for the information - have a Great New Year and Safe Boating

3pointstar